1. Field of the Invention
The present invention is directed to tubular coupling structures; protection rings for such structures; in one particular aspect, to combinations of a pipe coupling, a protective interior ring, and two pieces of pipe coupled together by the coupling; and to corrosion-resistant threaded connection parts and assemblies for use with clad or lined tubulars, e.g., but not limited to, oil and gas well tubing and casing, piping in chemical and other plants, oil and gas pipelines, and the like.
2. Background of the Related Art
Many tubulars are used to convey corrosive or erosive materials. Many piping systems and pipelines transport fluids that are highly corrosive to the carbon steel used in the pipe. In the drilling for and the production and injection of oil and gas, corrosion-resistant alloy pipe, e.g., casing or tubing, is now used in the drilling of oil and gas wells into zones that produce highly corrosive fluids. To overcome corrosion problems, and as well known to those skilled in the art, it is common to use lined steel pipe, with liners made of plastic, stainless steel, or other corrosion-resistant materials.
Certain typical multiple-walled pipe, e.g., a lined steel pipe, is a dual or double-walled pipe in which the inner wall is a liner tube made of a corrosion-resistant material that serves as a conductor for the corrosive fluid, and an outer wall or pipe that is designed to provide strength to withstand the internal pressures of the corrosive fluid, as well as external forces such as external pressure, mechanical loading, etc. In certain tubulars, there are limitations on the length of such double-walled pipes due to conditions to which the pipes are subjected on site. Thus, in the case of tubing or casing strings and in the production of oil and gas, each joint of pipe is usually about 24-44 feet long while the tubing or casing string itself may be thousands of feet long. Accordingly, and as is well known in making up such tubing or casing strings, successive joints of tubing/casing are connected together using couplings until the desired length of string is achieved. Similarly in pipelines successive pieces of pipe are joined by couplings.
It is desirable, where successive joints of the lined or clad pipe are joined to one another by means of a coupling that the interior of the coupling is protected from corrosion. Many prior art coupling and seal systems attempt an effective coupling structure e.g., and not by way of limitation, as disclosed in the subject matter of U.S. Pat. Nos. 590,811; 1,909,075; 2,040,786; 2,233,734; 2,805,872; 4,679,831; 5,282,652; 5,470,111; 5,689,871; 6,312,024; 6,863,313; and U.S. application Ser. No. 10/513,213 filed May 5, 2003, all of which patents are incorporated fully herein for all purposes.